(_Ornithorhynchus anatinus_)
For many years it was reported by the natives of Australia that the
extraordinary warm-blooded quadruped known to naturalists as the
duckbill, or platypus, produced its young from eggs laid in a burrow
by the female. That a mammal--and a mammal, although of an altogether
peculiar and out of the way type, the creature undoubtedly is--should
lay eggs was, however, too much for the minds of stay-at-home
naturalists, and the fiat accordingly went forth that the native story
was to be discredited. And discredited it therefore was. In nature, as
in other things, truth will, however, ultimately prevail; and we now
know for certain that the female lays in a burrow in the bank of some
river or pool a couple of hard-shelled, oval eggs, which in due course
hatch out into naked, helpless young, furnished with soft sucking lips.
Not that they suck in the ordinary mammalian fashion, for the female
platypus has no nipples, but her milk oozes out in the breast from a
number of sieve-like pores, from the surface of which it is sucked up
by her offspring.
Such a difference from the ordinary mammalian way of doing business
proclaims the wide distinction between the platypus, and, it may be
added, its relatives the spiny ant-eaters or echidnas (one of which
forms the subject of another illustration), and all other warm-blooded
quadrupeds. Nor is this all, for in the structure of their skeleton and
soft internal parts the platypus and the echidna display many marks of
affinity with reptiles and birds, which are totally wanting in other
mammals. These two creatures represent indeed a group by themselves, so
that mammals may be divided into two great primary sections, the one
embracing only the two egg-laying types, and the other all the rest.
And it is not a little significant that the egg-layers are confined
to Australia and New Guinea, the home of many other primitive and
ancient types which have disappeared from the rest of the world. In one
sense indeed the platypus and the echidna are not exactly primitive
creatures, as they have several specialised characters which were
evidently wanting in their ancestors. They may rather be described as
specialised branches of an ancient and primitive stock.
The duckbill is a heavily made aquatic mammal of about the size of a
very short-legged rabbit, with blackish, mole-like fur above, passing
gradually into whitish beneath, and a short, thick, tapering tail.
The very short limbs terminate in thick toes, connected together by a
web and armed with strong, pointed claws. In the fore-feet the margin
of the web projects considerably beyond the claws, but on the rare
occasions that the animal leaves the water the margin is folded
downward beneath the claws, so as to leave the claws exposed. In
museum-specimens, however, the web is almost invariably shown fully
expanded, as in the accompanying illustration; a condition in which it
would obviously be impossible for the animal to walk on land.
[Illustration]
The most remarkable external feature of the duckbill is undoubtedly
the duck-like, naked beak, pierced with two holes representing the
nostrils. In stuffed specimens, at any rate, this beak is dark-coloured
and horny in consistence, and looks as though it did not belong to the
animal, but in life it is soft and tender. Medium-sized, dark eyes
complete the physiognomy of this strange creature, in which external
ears are wanting.
The internal arrangements of the mouth of the duckbill are scarcely
less curious than the exterior. In early life the mouth is furnished,
both above and below, with three pairs of somewhat quadrangular
cheek-teeth, with raised and cusped margins. Beneath these grow up
certain large horny plates, and about the time that full maturity is
attained the teeth become worn out, and are finally shed, thus leaving
the horny plates as the sole masticating organs.
This replacement of the teeth by horny plates appears to be connected
with the nature of the food, for while in early life the duckbill
appears to subsist mainly on water insects and other comparatively soft
aquatic creatures, later on it takes to feeding almost entirely on
bivalve shells of one particular species; and for crushing the stout
shells of these molluscs it has been suggested that the tough horny
plates are better suited than brittle teeth.
Duckbills, except when in their burrows, pass the greater portion of
their time in the water, selecting quiet pools for their favourite
haunts. In such situations they may be seen on a still evening floating
and diving, and looking more like bottles in the water than anything
else. They obtain their food chiefly by probing in the mud with their
duck-like beaks. The dwelling-chamber of the burrow is situated in the
bank above the water level, but its entrance is below the surface,
although there is also an exit on the land. In the pairing-season the
males, which are armed with a poison-bearing spine on the inside of
each hind-leg, fight fiercely among themselves.
The duckbill, of which there is but a single species, is absolutely
confined to southern and eastern Australia and Tasmania; and its
nearest living relative is the echidna, of which a picture and notice
follow.